Pipes formed from thermoplastic materials including, but not limited to, polyethylene, polypropylene and PVC, are used in a variety of industries. To form a joint between sections of plastic pipe, the spigot end of one pipe is inserted within the bell or socket end of a second pipe. Such socket and spigot pipe joints between plastic pipes are well known in the art. For example, U.S. Pat. No. 3,539,205 discloses a pipe joint including a plastic pipe with a bell end portion further having an annular gasket seat portion for containing an annular gasket. The spigot end portion of another pipe is inserted into the bell end portion and through the annular gasket wherein the annular gasket forms a seal between the bell end portion and the spigot end portion. The use of a gasket not only improves the seal of the pipe joint, but also may allow a restrained or unrestrained pipe joint by the use of particular types of gaskets.
The formation of a thermoplastic pipe with a bell socket end containing a gasket cavity, however, typically requires the use of expensive machinery, such as expandable mandrels, to achieve the differential internal diameters of the bell socket. Therefore, a need exists for a less expensive methodology for the production of such thermoplastic pipes, which contain not only a bell socket end, but also a gasket cavity.